Photocatalytic oxidation of organic and biological molecules is one of the most efficient methods for alleviating the negative environmental impact of hazardous wastes and toxic pollutants in aqueousmedia. The superiority of photocatalytic technique in wastewater treatment is due to its advantages overthe traditional techniques such as quick oxidation, high efficiency, no formation of polycyclic products and oxidation of pollutants in the low levels [1].The process of photocatalysis is based on electron–holepairs created in semiconductor materials by the absorption of photons, which can further generate freeradicals such as hydroxyl in the system to redox the compounds absorbed on the surface of a photocatalyst. The use of solar irradiation to energize photocatalyst materials is environmentally appealing which permits the design of a simple, robust and inexpensive water treatment setup [2].In the present work, we have attempted to provide improvement in visible light photocatalytic activity of microwave synthesized ZnS and CdS nanoparticles via coating their surface by organic or inorganic materials. Microwave irradiation method is a facile and effective synthetic strategy to produce high purity perfect nanocrystals under mild conditions at reasonable cost and environmentally friendly [1]. The organic passivation of nanoparticles was performed using a water dispersible polymer, polyvinyl pyrrolidone (PVP), in a one pot reaction. For the inorganic passivation of ZnS and CdS nanoparticles, alayer of given thickness of CdS and ZnS, respectively, have been deposited on the surface ofnanoparticles using a two steps synthesis procedure. The obtained nanocomposites were characterized with several routine techniques and their photocatalytic performance was studied and compared by employing the photodegradation of methylene blue (MB) under visible light irradiation in terms of degradation efficiency and kinetic rate constant of photocatalysis.